Optical current transformer for gas-insulated apparatus

An optical current transformer for gas-insulated apparatus comprising:

• a sealed vessel filled with insulating gas;
• conductors for three-phase being arranged inside the sealed vessel, an hand hole being formed on a part of the sealed vessel, the hand hole being formed at only one location on the outer periphery of said sealed vessel;
• a sealed cover being placed on the each hand hole so as to close it;
• an optical fiber surrounding the conductor so as to form a closed loop, the optical fiber being hermetically led out to the outside of the sealed vessel through the sealed cover;
• at least a light source and an optical signal processor being provided on the lead out end of the optical fiber;
• an airtight hollow tube being disposed looping around the each conductors in the sealed vessel with a predefined separation distance;
• and
• a sealing/bonding means hermetically fixing between the end of the airtight hollow tube and the sealed cover, the end of the airtight hollow being routed to the hand hole side, and the airtight hollow has a configuration that the optical fiber can be inserted therethrough.